If you need written permission from the government to exercise your right, it’s not a right. According to the lawsuit they were in the park for an hour before security made first contact. The event didn’t occupy the entire park so they were within their rights to be wherever they wanted outside the ticketed area.

Here’s an on-point example

https://www.lp.org/conn-libertarians-receive-37k-settlement-in-petitioner-harassment-suit/